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==Why is it Important?==

==Why is it Important?==

Sodium is indispensable for the '''regulation of acid-base balance and osmotic pressure'''. Its other main role is maintaining the membrane potential in nerve and muscle tissues thereby facilitating the generation and transmission of electrical impulses.

Sodium is indispensable for the '''regulation of [[Essential Ion and Compound Balance and Homeostasis - Anatomy & Physiology|acid base balance]] and osmotic pressure'''. Its other main role is maintaining the membrane potential in nerve and muscle tissues thereby facilitating the generation and transmission of electrical impulses.

==Roles in the Body==

==Roles in the Body==

Sodium is distributed in [[Bones - Anatomy & Physiology|bone]] (43%) interstitial fluid (29%) and [[plasma]] (12%). The concentration of sodium (i.e., sodium chloride) in blood is approximately 0.9%. The main hormone involved in sodium balance is '''[[aldosterone]]''', which is released by the [[Adrenal Glands - Anatomy & Physiology|adrenal glands]] in response to a low plasma sodium concentration. Aldosterone acts by increasing the renal retention of sodium.

Sodium is distributed in [[Bones - Anatomy & Physiology|bone]] (43%) interstitial fluid (29%) and [[plasma]] (12%). The concentration of sodium (i.e., sodium chloride) in blood is approximately 0.9%. The main hormone involved in sodium balance is '''[[aldosterone]]''', which is released by the [[Adrenal Glands - Anatomy & Physiology|adrenal glands]] in response to a low plasma sodium concentration. Aldosterone acts by increasing the renal retention of sodium.

The high level of sodium in extracellular fluids is responsible for establishing a concentration gradient across cell membranes. Sodium attracts water molecules when in solution, and the size of the hydrated sodium ion prevents it crossing cell membranes as easily as other ions such as [[Potassium - Nutrition|potassium]] and [[Chloride - Nutrition|chloride]]. This means that the permeability of the membrane to sodium is generally very low but when there is a momentary change in the membrane’s permeability, sodium is driven into the cell and this dramatically alters the membrane potential from negative to positive. This change – the '''action potential''' – is responsible for nervous activity. The extra sodium in the cell is then removed by active transport via a sodium pump, which is energy dependent, and this restores the system to its resting state.

The high level of sodium in extracellular fluids is responsible for establishing a concentration gradient across cell membranes. Sodium attracts water molecules when in solution, and the size of the hydrated sodium ion prevents it crossing cell membranes as easily as other ions such as [[Potassium - Nutrition|potassium]] and [[Chloride - Nutrition|chloride]]. This means that the permeability of the membrane to sodium is generally very low but when there is a momentary change in the membrane’s permeability, sodium is driven into the cell and this dramatically alters the membrane potential from negative to positive. This change – the [[Neurons - Anatomy & Physiology#Nerve Impulse Propagation|'''action potential''']] – is responsible for nervous activity. The extra sodium in the cell is then removed by active transport via a sodium pump, which is energy dependent, and this restores the system to its resting state.

==Consequences of Sodium Deficiency==

==Consequences of Sodium Deficiency==

The main adverse effect of excessive sodium intake is an '''increased potassium excretion resulting in a negative potassium balance'''. A sodium content of 2.9% DM fed to adult dogs caused [[vomiting]] and food aversion<ref>Zentek, J, Meyer, H (1995). “Normal handling of diets – Are all dogs created equal?”. J. Sm. Anim. Pract. 36:354-359.  </ref>. However, given an adequate supply of water, dogs can cope with a wide range of sodium intakes and dietary levels up to 1.5% DM are deemed acceptable<ref>Boemke, W, Palm, U, Kaczmarczyk, G, Reinhardt, H (1990). “Effect of high sodium and high water intake on 24-h potassium balance in dogs”. J. Exper. Anim. Sci. 33:179-185.</ref>.

The main adverse effect of excessive sodium intake is an '''increased potassium excretion resulting in a negative potassium balance'''. A sodium content of 2.9% DM fed to adult dogs caused [[vomiting]] and food aversion<ref>Zentek, J, Meyer, H (1995). “Normal handling of diets – Are all dogs created equal?”. J. Sm. Anim. Pract. 36:354-359.  </ref>. However, given an adequate supply of water, dogs can cope with a wide range of sodium intakes and dietary levels up to 1.5% DM are deemed acceptable<ref>Boemke, W, Palm, U, Kaczmarczyk, G, Reinhardt, H (1990). “Effect of high sodium and high water intake on 24-h potassium balance in dogs”. J. Exper. Anim. Sci. 33:179-185.</ref>.

====Cat:====   

====Cat:====   

There is little if any information on the adverse effects of high sodium intakes in cats. Yu et al.<ref>Yu, S, Rogers, Q, Morris, J (1997). “Absence of salt (NaCl) preference or appetite in sodium-replete or depleted kittens”. Appetite 29:1-10.</ref> reported that, although kittens showed an aversion to a diet containing sodium at 1% DM when given a choice, they consumed it in normal amounts with no adverse effects when it was the only diet available. Burger<ref>Burger, I (1979). “Water balance in the dog and cat”. Pedigree Digest 6:10-11.</ref> reported that adult cats receiving dietary sodium up to 1.5% DM showed no abnormalities. These values are similar to those reported for dogs and, as with dogs, assume adequate amounts of water are available.

There is little if any information on the adverse effects of high sodium intakes in cats. Yu ''et al''.<ref>Yu, S, Rogers, Q, Morris, J (1997). “Absence of salt (NaCl) preference or appetite in sodium-replete or depleted kittens”. Appetite 29:1-10.</ref> reported that, although kittens showed an aversion to a diet containing sodium at 1% DM when given a choice, they consumed it in normal amounts with no adverse effects when it was the only diet available. Burger<ref>Burger, I (1979). “Water balance in the dog and cat”. Pedigree Digest 6:10-11.</ref> reported that adult cats receiving dietary sodium up to 1.5% DM showed no abnormalities. These values are similar to those reported for dogs and, as with dogs, assume adequate amounts of water are available.

==Dietary Sources==

==Dietary Sources==

==References==

==References==

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[[Category:To Do - Nutrition GGP]]

[[Category:Minerals in Nutrition]]